The invention generally relates to suspension systems, and more particularly to an improved suspension system including an air-bag assembly and a leaf-spring assembly interconnected in a manner such that the suspension system is responsive to changes in the weight of a load for varying the configuration of the suspension system between a hard-ride configuration, wherein the bag is substantially collapsed, and thus rendered ineffective for absorbing shock loads, and an empty-ride configuration wherein the air bag is expanded for absorbing shock loads. The term hard-ride configuration, as herein employed, refers to a configuration for a vehicle suspension system wherein the air bag of the included air-bag assembly is collapsed and thus rendered inoperative for absorbing shock loads, while the term empty-ride refers to a configuration for the suspension system wherein the air bag is expanded and thus rendered operative for absorbing shock loads and thereby isolating, at least in part, the frame of the vehicle from highway induced vibratory motion transmitted thereto from the wheels of the vehicle.
As is readily recognized by those familiar with the design of suspension systems for vehicles such as trucks, trailers and the like, a suspension system should be sufficiently resilient for absorbing shock loads resulting from highway induced vibration. In order to achieve this result, it heretofore has been common practice to provide massive springs interposed between the load-bearing axles and the frames of such vehicles. While springs of sufficient rigidity can readily be provided, for supporting a vehicle in its loaded condition, by increasing the mass thereof, a perplexing problem arises when the vehicle must be transported in its unloaded or empty condition.
For example, it is not unusual for a trailer, such as a flatbed or the like, to be employed in transporting a load to a given destination and thereafter be returned in its empty condition. Of course, where the springs employed are sufficiently rigid for supporting the trailer in its loaded condition, the springs often lack sufficient resiliency for dissipating shock loads when the trailer is transported at high speed in its unloaded condition. Consequently, such vehicles often are subjected to destructive effects of shock loading, resulting from highway induced rebound, as the vehicles are transported in an unloaded condition.
Attempts have been made to solve this and similar problems employing various techniques including a use of leaf springs combined with air bags, frequently referred to as air springs. Such suspension systems are typified by the system disclosed in U.S. Pat. No. 3,309,107 and U.S. Pat. No. 3,294,390.
While these systems generally have met with varying degrees of acceptance, they have not provided a total solution to the problem, particularly since designers must continuously cope with problems arising out of limitations placed on bulk, mass and complexity due to economic considerations found in both the trucking and manufacturing industries.
It is, therefore, the general purpose of the instant invention to provide an improved and simplified suspension system capable of achieving automatic and positive conversion between hard-ride and empty-ride configurations, in response to changes in the weight of loads applied to the frame of a vehicle supported thereby.